1. Field of the Invention
The present invention relates to an optical disk recording and reproducing device for recording and reproducing information on an optical disk. In particular, the present invention relates to an optical disk recording and reproducing device having a function of instructing backup of the optical disk before data recorded on it becomes unable to be read due to a scratch on its recording surface, alteration of dye or the like.
2. Description of Related Art
Recently, a digital versatile disk (DVD) that is an optical disk capable of recording a large quantity of video and audio data such as a movie has become commonplace. There are several types of the DVD includes a DVD-ROM that stores information recorded on a manufacture's side and cannot be rewritten on a user's side, a DVD-R and a DVD+R on which information can be written only once on the user's side, and a DVD-RW, a DVD+RW and a DVD-RAM on which information can be rewritten a predetermined number of times on the user's side. Information recorded on the DVD can be reproduced by using an optical disk reproducing device (i.e., a DVD player) or an optical disk recording and reproducing device (i.e., a DVD recorder), and information can be recorded on the DVD-R, the DVD+R, the DVD-RW, the DVD+RW or the DVD-RAM by using the optical disk recording and reproducing device.
When the conventional optical disk recording and reproducing device reproduces data recorded on an optical disk, it converts an RF signal that is a read signal from an optical pickup into digital data and then performs a signal modulating process and an error correcting process by ECC block in accordance with a data format of the DVD. This error correcting process is performed as an error correcting function that enables some extent of data losses to be recovered. In addition, as to data of pictures or music, data correction can be performed by data interpolation to an extent such that a user does not notice the defect even if the defect cannot be recovered completely by the error correcting function.
Although deterioration of analog data recorded on a magnetic tape like a video cassette tape can be sensed by a user when the reproduced image is deteriorated due to the deterioration of the magnetic tape, it is difficult for a user to perceive deterioration of digital data recorded on an optical disk such as a DVD even if it has a scratch on the recording surface or alteration of dye, because of the error correcting process. Accordingly, the user may happen to have the optical disk on which data cannot be read suddenly. It is necessary, therefore, for the user to back up the data recorded on the optical disk by the optical disk recording and reproducing device before the data recorded on the optical disk becomes unable to be read.
A conventional device disclosed in JP-A-2005-25861, for example, detects deterioration of an optical disk by checking an error level of data read from the optical disk and informs a user of the deterioration so that the data can be backed up in a free space of the optical disk. However, it does not detect a jitter value of the read signal from the optical pickup. Therefore, the deteriorated situation of the optical disk on the time scale cannot be grasped. In other words, it is difficult to know whether the deterioration has been generated gradually or abruptly, so the user cannot prepare or take measures for the backup in advance.